Zoom lens system, interchangeable lens apparatus and camera system

ABSTRACT

Provided is a zoom lens system including a compact focusing lens unit and having a suppressed change in image magnification at the time of movement of the focusing lens unit. A zoom lens system of the present invention, in order from an object side to an image side, includes, a first lens unit G 1  having negative optical power, a second lens unit G 2  having positive optical power, a third lens unit G 3  having positive optical power, and a fourth lens G 4.  Condition (10): 1.4&lt;DL/YM&lt;2.5 and condition (11): 1.2&lt;BF W /YM&lt;1.6 are satisfied (where, 100&lt;2ω W &lt;140, DL is an effective diameter of the lens surface closest to the image side, BF W  is the back focus at a wide-angle limit, YM is the maximum image height at a wide-angle limit, and ω W  is a half view angle (°) at a wide-angle limit).

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2009-021834filed on Feb. 2, 2009. Hereby, the contents of Japanese PatentApplication No. 2009-021834 are incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens system and, in particular,to a zoom lens system suitable for an imaging lens system employed in aninterchangeable lens apparatus in a so-called interchangeable-lens typedigital camera system. Further, the present invention relates to aninterchangeable lens apparatus and a camera system that employ this zoomlens system.

2. Description of the Background Art

In recent years, interchangeable-lens type digital camera systems arerapidly spreading. The interchangeable-lens type digital camera system(also simply referred to as “camera system”) is a camera systemincluding: a camera body employing an image sensor composed of a CCD(Charge Coupled Device), a CMOS (Complementary Metal-OxideSemiconductor), or the like; and an interchangeable lens apparatusemploying an imaging lens system for forming an optical image on thelight acceptance surface of the image sensor. Zoom lens systemsapplicable to the above interchangeable-lens type digital camera aredisclosed in Japanese Laid-Open Patent Publication No. 2005-284097,Japanese Laid-Open Patent Publication No. 2005-352057, JapaneseLaid-Open Patent Publication No. 2006-221092, Japanese Laid-Open PatentPublication No. 2005-316396, Japanese Laid-Open Patent Publication No.2006-267425, Japanese Laid-Open Patent Publication No. 2007-219315,Japanese Laid-Open Patent Publication No. 2008-3195, and JapaneseLaid-Open Patent Publication No. 2008-15251.

On the other hand, there are interchangeable-lens type digital camerasystems employing a function of displaying image data generated by theimaging lens system or the image sensor on a display unit such as aliquid crystal display or the like of a camera body (hereinafterreferred to as “live view function”) (e.g., Japanese Laid-Open PatentPublication No. 2000-111789 and Japanese Laid-Open Patent PublicationNo. 2000-333064).

SUMMARY OF THE INVENTION

In the camera system disclosed in Japanese Laid-Open Patent PublicationNo. 2000-111789 and Japanese Laid-Open Patent Publication No.2000-333064, when the live view function is being performed, a contrastAF method is employed to perform focusing operation. The contrast AF isthe focusing operation based on the contrast value of image dataobtained from the image sensor. Hereinafter, an operation of thecontrast AF will be described.

First, the camera system oscillates the focusing lens unit in theoptical axis direction at a high-speed (hereinafter referred to as“wobbling”) thereby to detect the direction of displacement from anin-focus condition. After the wobbling, the camera system detects, froman output signal of the image sensor, signal components in apredetermined frequency band in an image region and calculates anoptimal position of the focusing lens unit for realizing the in-focuscondition. Thereafter, the camera system moves the focusing lens unit tothe optimal position, and completes the focusing operation. When thefocusing operation is performed continuously in video image taking orthe like, the camera system repeats a series of the above operations.

Generally, in order that uneasiness such as flickers should be avoided,video displaying need be performed at a high rate of, for example, 30frames per second. Thus, basically, video image taking using theinterchangeable-lens type digital camera also need be performed at thesame rate of 30 frames per second. Accordingly, the focusing lens unitneed be driven at the high rate of 30 Hz at the time of wobbling.

However, if the weight of the focusing lens unit is large, a largermotor or actuator is required to move the focusing lens unit at a highrate. This causes a problem that the outer diameter of the lens barrelis increased. However, in the case of the zoom lens systems disclosed inthe above conventional arts, the focusing lens unit is hardlylight-weighted.

Further, in the interchangeable-lens type digital camera, it should benoted that the size of the image corresponding to a photographic objectvaries in association with wobbling. This variation in the image iscaused mainly by the fact that the movement of the focusing lens unit inthe optical axis direction generates a change in the focal length of theentire lens system. Then, when a large change in the image takingmagnification is generated in association with wobbling, the imagetaking person will feel uneasiness.

An object of the present invention is to provide a zoom lens systemwhich includes a compactly constructed focusing lens unit and which hasa suppressed change in the image magnification at the time of movementof the focusing lens unit, and an interchangeable lens apparatus and acamera system which employ this zoom lens system.

A zoom lens system according to the present invention includes aplurality of lens units and performs zooming by changing intervals amongthe lens units. The plurality of lens units, in order from an objectside to an image side, includes: a first lens unit having negativeoptical power; a second lens unit having positive optical power; a thirdlens unit having positive optical power; and a fourth lens. Thefollowing conditions are satisfied:

1.4<DL/YM<2.5  (10)

1.2<BF_(W) /YM<1.6  (11)

(where, 100<2ω_(W)<140)

where,

DL is an effective diameter of the lens surface closest to the imageside,

BF_(W) is the back focus at a wide-angle limit,

YM is the maximum image height at a wide-angle limit, and

ω_(W) is a half view angle (°) at a wide-angle limit.

An interchangeable lens apparatus according to the present inventionincludes: any of the above zoom lens system, and a mount sectionconnected to a camera body that includes an image sensor which receivesan optical image formed by the zoom lens system thereby to convert theoptical image to an electrical image signal.

A camera system according to the present invention includes: aninterchangeable lens apparatus that includes any of the above zoom lenssystem, and a camera body which is connected to the interchangeable lensapparatus via a camera mount section in an attachable and removablemanner and includes an image sensor which receives an optical imageformed by the zoom lens system thereby to convert the optical image toan electrical image signal.

According to the present invention, it is possible to provide a zoomlens system which includes a compactly constructed focusing lens unitand which has a suppressed change in image magnification at the time ofmovement of the focusing lens unit, and an interchangeable lensapparatus and a camera system which employ the zoom lens system.

These and other objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 1 (Example 1);

FIG. 2 is a longitudinal aberration diagram showing an infinity in-focuscondition of a zoom lens system according to Example 1;

FIG. 3 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 2 (Example 2);

FIG. 4 is a longitudinal aberration diagram showing an infinity in-focuscondition of a zoom lens system according to Example 2;

FIG. 5 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 3 (Example 3);

FIG. 6 is a longitudinal aberration diagram showing an infinity in-focuscondition of a zoom lens system according to Example 3;

FIG. 7 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 4 (Example 4);

FIG. 8 is a longitudinal aberration diagram showing an infinity in-focuscondition of a zoom lens system according to Example 4;

FIG. 9 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 5 (Example 5);

FIG. 10 is a longitudinal aberration diagram showing an infinityin-focus condition of a zoom lens system according to Example 5;

FIG. 11 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 6 (Example 6);

FIG. 12 is a longitudinal aberration diagram showing an infinityin-focus condition of a zoom lens system according to Example 6; and

FIG. 13 is a schematic construction diagram of an interchangeable-lenstype digital camera system according to Embodiment 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1, 3, 5, 7, 9, and 11 show lens arrangement diagrams of zoom lenssystems according to Embodiments 1, 2, 3, 4, 5, and 6, respectively, andeach show a zoom lens system in a infinity in-focus condition.

In each diagram, part (a) shows a lens configuration at a wide-anglelimit (in the minimum focal length condition: focal length f_(W)), part(b) shows a lens configuration at a middle position (in an intermediatefocal length condition: focal length f_(M)=√(f_(W)*f_(T))), and part (c)shows a lens configuration at a telephoto limit (in the maximum focallength condition: focal length f_(T)). Further, in each diagram, eachbend arrow located between part (a) and part (b) indicates a lineobtained by connecting the positions of the lens units respectively at awide-angle limit, a middle position, and a telephoto limit, in orderfrom the top. In the part between the wide-angle limit and the middleposition, and the part between the middle position and the telephotolimit, the positions are connected simply with a straight line, andhence this line does not indicate actual motion of each lens unit.Moreover, in each diagram, an arrow imparted to a lens unit indicatesfocusing from an infinity in-focus condition to a close-object in-focuscondition. That is, the arrow indicates the moving direction at the timeof focusing from an infinity in-focus condition to a close-objectin-focus condition.

In FIGS. 1, 3, 5, 7, 9, and 11, asterisk “*” imparted to a particularsurface indicates that the surface is aspheric. Further, in eachdiagram, symbol (+) or symbol (−) imparted to the symbol of each lensunit corresponds to the sign of the optical power of the lens unit.Still further, in each diagram, the straight line located on the mostright-hand side indicates the position of the image surface S. Stillfurther, in each diagram, the straight line located between adjoininglens elements indicates the position of an aperture diaphragm A.

Embodiment 1

The zoom lens system according to Embodiment 1, in order from the objectside to the image side, includes a first lens unit G1 having negativeoptical power, a second lens unit G2 having positive optical power, athird lens unit G3 having positive optical power, a fourth lens unit G4having negative optical power, and a fifth lens unit G5 having positiveoptical power.

The first lens unit G1, in order from the object side to the image side,includes: a negative meniscus first lens element L1 with the convexsurface facing the object side; a negative meniscus second lens elementL2 with the convex surface facing the object side; a negative meniscusthird lens element L3 with the convex surface facing the object side; abi-concave fourth lens element L4; and a positive meniscus fifth lenselement L5 with the convex surface facing the object side. A surface ofthe third lens element L3 facing the image side is aspheric.

The second lens unit G2, in order from the object side to the imageside, includes: a negative meniscus sixth lens element L6 with theconvex surface facing the object side; and a positive meniscus seventhlens element L7 with the convex surface facing the object side. Thesixth lens element L6 and the seventh lens element L7 are cemented witheach other.

The third lens unit G3, in order from the object side to the image side,includes: a negative meniscus eighth lens element L8 with the convexsurface facing the object side; a bi-convex ninth lens element L9; abi-concave tenth lens element L10; a bi-convex eleventh lens elementL11; a positive meniscus twelfth lens element L12 with the convexsurface facing the image side; and a bi-convex thirteenth lens elementL13. The eighth lens element L8 and the ninth lens element L9 arecemented with each other. In addition, the tenth lens element L10 andthe eleventh lens element L11 are cemented with each other.

The fourth lens unit G4 consists of a negative meniscus fourteenth lenselement L14 with the convex surface facing the object side.

The fifth lens unit G5, in order from the object side to the image side,includes: a negative meniscus fifteenth lens element L15 with the convexsurface facing the object side; and a bi-convex sixteenth lens elementL16. The fifteenth lens element L15 and the sixteenth lens element L16are cement with each other. A surface of the sixteenth lens element L16facing the image side is aspheric.

At the time of zooming, the plurality of lens units move along theoptical axis such that: the interval between the first lens unit G1 andthe second lens unit G2 at a telephoto limit is made shorter than theinterval at a wide-angle limit; the interval between the second lensunit G2 and the third lens unit G3 at a telephoto limit is made shorterthan the interval at a wide-angle limit; the interval between the thirdlens unit G3 and the fourth lens unit G4 at a telephoto limit is madeshorter than the interval at a wide-angle limit; and the intervalbetween the fourth lens unit G4 and the fifth lens unit G5 at atelephoto limit is made longer than the interval at a wide-angle limit.More specifically, at the time of zooming from a wide-angle limit to atelephoto limit, the first lens unit G1 moves to the image side alongthe optical axis, whereas the second lens unit G2, the third lens unitG3, and the fourth lens unit G4 move to the object side along theoptical axis. The fifth lens unit G5 is fixed relative to the imagesurface S at the time of zooming. The aperture diaphragm A moves to theobject side together with the second lens unit G2.

Further, at the time of focusing from an infinity in-focus condition toa close-point in-focus condition, the fourth lens unit G4 moves to theimage side along the optical axis.

Embodiment 2

The zoom lens system according to Embodiment 2, in order from the objectside to the image side, includes a first lens unit G1 having negativeoptical power, a second lens unit G2 having positive optical power, athird lens unit G3 having positive optical power, a fourth lens unit G4having negative optical power, and a fifth lens unit G5 having positiveoptical power.

The first lens unit G1, in order from the object side to the image side,includes: a negative meniscus first lens element L1 with the convexsurface facing the object side; a negative meniscus second lens elementL2 with the convex surface facing the object side; a negative meniscusthird lens element L3 with the convex surface facing the object side; abi-concave fourth lens element L4; and a positive meniscus fifth lenselement L5 with the convex surface facing the object side. The fourthlens element L4 and the fifth lens element L5 are cemented with eachother. Further, a surface of the third lens element L3 facing the imageside is aspheric.

The second lens unit G2, in order from the object side to the imageside, includes: a negative meniscus sixth lens element L6 with theconvex surface facing the object side; and a positive meniscus seventhlens element L7 with the convex surface facing the object side. Thesixth lens element L6 and the seventh lens element L7 are cemented witheach other.

The third lens unit G3, in order from the object side to the image side,includes: a negative meniscus eighth lens element L8 with the convexsurface facing the object side; a bi-convex ninth lens element L9; abi-concave tenth lens element L10, a bi-convex eleventh lens elementL11, a positive meniscus twelfth lens element L12 with the convexsurface facing the image side; and a bi-convex thirteenth lens elementL13. The eighth lens element L8 and the ninth lens element L9 arecemented with each other. In addition, the tenth lens element L10 andthe eleventh lens element L11 are cemented with each other.

The fourth lens unit G4 consists of a negative meniscus fourteenth lenselement L14 with the convex surface facing the object side.

The fifth lens unit G5, in order from the object side to the image side,includes: a negative meniscus fifteenth lens element L15 with the convexsurface facing the object side; and a bi-convex sixteenth lens elementL16. The fifteenth lens element L15 and the sixteenth lens element L16are cemented with each other. Further, a surface of the sixteenth lenselement L16 facing the image side is aspheric.

At the time of zooming, the plurality of lens units move along theoptical axis such that: the interval between the first lens unit G1 andthe second lens unit G2 at a telephoto limit is made shorter than theinterval at a wide-angle limit; the interval between the second lensunit G2 and the third lens unit G3 at a telephoto limit is made shorterthan the interval at a wide-angle limit; the interval between the thirdlens unit G3 and the fourth lens unit G4 at a telephoto limit is madeshorter than the interval at a wide-angle limit; and the intervalbetween the fourth lens unit G4 and the fifth lens unit G5 at atelephoto limit is made longer than the interval in a wide-angle limit.More specifically, at the timing of zooming from a wide-angle limit to atelephoto limit, the first lens unit G1 moves to the image side alongthe optical axis, whereas the second lens unit G2, third lens unit G3,and the fourth lens unit G4 move to the object side along the opticalaxis. The fifth lens unit G5 is fixed relative to the image surface S atthe time of zooming. The aperture diaphragm A moves to the object sidetogether with the second lens unit G2.

Further, at the time of focusing from an infinity in-focus condition toa close-point in-focus condition, the fourth lens unit G4 moves to theimage side along the optical axis.

Embodiment 3

The zoom lens system according to Embodiment 3, in order from the objectside to the image side, includes: a first lens unit G1 having negativeoptical power, a second lens unit G2 having positive optical power, athird lens unit G3 having positive optical power, a fourth lens unit G4having negative optical power, and a fifth lens unit G5 having positiveoptical power.

The first lens unit G1, in order from the object side to the image side,includes: a negative meniscus first lens element L1 with the convexsurface facing the object side; a negative meniscus second lens elementL2 with the convex surface facing the object side; a negative meniscusthird lens element L3 with the convex surface facing the object side; abi-concave fourth lens element L4; and a positive meniscus fifth lenselement L5 with the convex surface facing the object side. The fourthlens element L4 and the fifth lens element L5 are cemented with eachother. A surface of the third lens element L3 facing the image side isaspheric.

The second lens unit G2, in order from the object side to the imageside, includes: a negative meniscus sixth lens element L6 with theconvex surface facing the object side; and a positive meniscus seventhlens element L7 with the convex surface facing the object side. Thesixth lens element L6 and the seventh lens element L7 are cemented witheach other.

The third lens unit G3, in order from the object side to the image side,includes: a plano-concave eighth lens element L8 with the concavesurface facing the image side; a bi-convex ninth lens element L9; abi-concave tenth lens element L10; a bi-convex eleventh lens elementL11; and a bi-convex twelfth lens element L12. The eighth lens elementL8 and the ninth lens element L9 are cemented with each other. Inaddition, the tenth lens element L10 and the eleventh lens element L11are cemented with each other.

The fourth lens unit G4 consists of a negative meniscus thirteenth lenselement L13 with the convex surface facing the object side.

The fifth lens unit G5, in order from the object side to the image side,includes: a bi-concave fourteenth lens element L14; and a bi-convexfifteenth lens element L15. The fourteenth lens element L14 and thefifteenth lens element L15 are cemented with each other. Further, asurface of the fifteenth lens element L15 facing the image side isaspheric.

At the time of zooming, the plurality of lens units move along theoptical axis such that: the interval between the first lens unit G1 andthe second lens unit G2 at a telephoto limit is made shorter than theinterval at a wide-angle limit; the interval between the second lensunit G2 and the third lens unit G3 at a telephoto limit hardly changesfrom the interval at a wide-angle limit; the interval between the thirdlens unit G3 and the fourth lens unit G4 at a telephoto limit is madeshorter than the interval at a wide-angle limit; and the intervalbetween the fourth lens unit G4 and the fifth lens unit G5 at atelephoto limit is made longer than the interval at a wide-angle limit.More specifically, at the time of zooming from a wide-angle limit to atelephoto limit, the first lens unit G1 moves to the image side alongthe optical axis, whereas the second lens unit G2, the third lens unitG3, and the fourth lens unit G4 move to the object side along theoptical axis. The fifth lens unit G5 is fixed relative to the imagesurface S at the time of zooming. The aperture diaphragm A moves to theobject side together with the second lens unit G2.

Further, at the time of focusing from an infinity in-focus condition toa close-point in-focus condition, the fourth lens unit G4 moves to theimage side along the optical axis.

Embodiment 4

The zoom lens system according to Embodiment 4, in order from the objectside to the image side, includes a first lens unit G1 having negativeoptical power, a second lens unit G2 having positive optical power, athird lens unit G3 having positive optical power, a fourth lens unit G4having negative optical power, and a fifth lens unit G5 having positiveoptical power.

The first lens unit G1, in order from the object side to the image side,includes: a negative meniscus first lens element L1 with the convexsurface facing the object side; a negative meniscus second lens elementL2 with the convex surface facing the object side; a negative meniscusthird lens element L3 with the convex surface facing the object side; anbi-concave fourth lens element L4; and a positive meniscus fifth lenselement L5 with the convex surface facing the object side. The fourthlens element L4 and the fifth lens element L5 are cemented with eachother. Further, a surface of the third lens element L3 facing the imageside is aspheric.

The second lens unit G2, in order from the object side to the imageside, includes: a negative meniscus sixth lens element L6 with theconvex surface facing the object side; and a positive meniscus seventhlens element L7 with the convex surface facing the object side. Thesixth lens element L6 and the seventh lens element L7 are cemented witheach other. A surface of the seventh lens element L7 facing the imageside is aspheric.

The third lens unit G3, in order from the object side to the image side,includes: a negative meniscus eighth lens element L8 with the convexsurface facing the object side; a bi-convex ninth lens element L9; abi-concave tenth lens element L10; a bi-convex eleventh lens elementL11; and a bi-convex twelfth lens element L12. The eighth lens elementL8 and the ninth lens element L9 are cemented with each other. Inaddition, the tenth lens element L10 and the eleventh lens element L11are cemented with each other.

The fourth lens unit G4 consists of a negative meniscus thirteenth lenselement L13 with the convex surface facing the object side.

The fifth lens unit G5, in order from the object side to the image side,includes: a bi-concave fourteenth lens element L14; and a bi-convexfifteenth lens element L15. The fourteenth lens element L14 and thefifteenth lens element L15 are cemented with each other. Further, asurface of the fifteenth lens element L15 facing the image side isaspheric.

At the time of zooming, the plurality of lens units move along theoptical axis such that: the interval between the first lens unit G1 andthe second lens unit G2 at a telephoto limit is made shorter than theinterval at a wide-angle limit; the interval between the second lensunit G2 and the third lens unit G3 at a telephoto limit is made shorterthan the interval at a wide-angle limit; the interval between the thirdlens unit G3 and the fourth lens unit G4 at a telephoto limit hardlychanges from the interval at a wide-angle limit; and the intervalbetween the fourth lens unit G4 and the fifth lens unit G5 at atelephoto limit is made longer than the interval at a wide-angle limit.More specifically, at the time of zooming from a wide-angle limit to atelephoto limit, the first lens unit G1 moves to the image side alongthe optical axis, whereas the second lens unit G2, the third lens unitG3, and the fourth lens unit G4 move to the object side along theoptical axis. The fifth lens unit G5 is fixed relative to the imagesurface S at the time of zooming. The aperture diaphragm A moves to theobject side together with the second lens unit G2.

Further, at the time of focusing from an infinity in-focus condition toa close-point in-focus condition, the fourth lens unit G4 moves to theimage side along the optical axis.

Embodiment 5

The zoom lens system according to Embodiment 5, in order from the objectside to the image side, includes, a first lens unit G1 having negativeoptical power, a second lens unit G2 having positive optical power, athird lens unit G3 having positive optical power, a fourth lens unit G4having negative optical power, and a fifth lens unit G5 having positiveoptical power.

The first lens unit G1, in order from the object side to the image side,includes: a negative meniscus first lens element L1 with the convexsurface facing the object side; a negative meniscus second lens elementL2 with the convex surface facing the object side; a negative meniscusthird lens element L3 with the convex surface facing the object side; abi-concave fourth lens element L4; and a positive meniscus fifth lenselement L5 with the convex surface facing the object side. The fourthlens element L4 and the fifth lens element L5 are cemented with eachother. A surface of the third lens element L3 facing the image side isaspheric.

The second lens unit G2, in order from the object side to the imageside, includes: a negative meniscus sixth lens element L6 with theconvex surface facing the object side; and a positive meniscus seventhlens element L7 with the convex surface facing the object side. Thesixth lens element L6 and the seventh lens element L7 are cemented witheach other. Further, a surface of the seventh lens element L7 facing theimage side is aspheric.

The third lens unit G3, in order from the object side to the image side,includes: a bi-concave eighth lens element L8; a bi-convex ninth lenselement L9; a bi-concave tenth lens element L10; a bi-convex eleventhlens element L11; and a bi-convex twelfth lens element L12. The eighthlens element L8 and the ninth lens element L9 are cemented with eachother. In addition, the tenth lens element L10 and the eleventh lenselement L11 are cemented with each other.

The fourth lens unit G4 consists of a negative meniscus thirteenth lenselement L13 with the convex surface facing the object side.

The fifth lens unit G5, in order from the object side to the image side,includes: a negative meniscus fourteenth lens element L14 with theconvex surface facing the object side; and a bi-convex fifteenth lenselement L15. A surface of the fifteenth lens element L15 facing theimage side is aspheric.

At the time of zooming, the plurality of lens units move along theoptical axis such that: the interval between the first lens unit G1 andthe second lens unit G2 at a telephoto limit is made shorter than theinterval at a wide-angle limit; the interval between the second lensunit G2 and the third lens unit G3 at a telephoto limit is made shorterthan the interval at a wide-angle limit; the interval between the thirdlens unit G3 and the fourth lens unit G4 at a telephoto limit hardlychanges from the interval at a wide-angle limit; and the intervalbetween the fourth lens unit G4 and the fifth lens unit G5 at atelephoto limit is made longer than the interval at a wide-angle limit.More specifically, at the time of zooming from a wide-angle limit to atelephoto limit, the first lens unit G1 moves to the image side alongthe optical axis, whereas the second lens unit G2, the third lens unitG3, and the fourth lens unit G4 move to the object side along theoptical axis. The fifth lens unit G5 is fixed relative to the imagesurface S at the time of zooming. The aperture diaphragm A moves to theobject side together with the second lens unit G2.

Further, at the time of focusing from an infinity in-focus condition toa close-point in-focus condition, the fourth lens unit G4 moves to theimage side along the optical axis.

Embodiment 6

The zoom lens system according to Embodiment 6, in order from the objectside to the image side, includes a first lens unit G1 having negativeoptical power, a second lens unit G2 having positive optical power, athird lens unit G3 having positive optical power, and a fourth lens unitG4 having positive optical power.

The first lens unit G1, in order from the object side to the image side,includes: a negative meniscus first lens element L1 with the convexsurface facing the object side; a negative meniscus second lens elementL2 with the convex surface facing the object side; a negative meniscusthird lens element L3 with the convex surface facing the object side; anegative meniscus fourth lens element L4 with the convex surface facingthe image side; and a positive meniscus fifth lens element L5 with theconvex surface facing the object side. A surface of the second lenselement L2 facing the object side and a surface of the fourth lenselement L4 facing the image side are aspheric.

The second lens unit G2 consists of a bi-convex sixth lens elements L6.Both surfaces of the six lens element L6 are aspheric.

The third lens unit G3, in order from the object side to the image side,includes: a bi-convex seventh lens element L7; a bi-concave eighth lenselement L8; a bi-convex ninth lens element L9; a bi-convex tenth lenselement L10; a bi-concave eleventh lens element L11; a bi-convex twelfthlens element L12; and a positive meniscus thirteenth lens element L13with the convex surface facing the image side. The seventh lens elementL7, the eighth lens element L8, and the ninth lens element L9 arecemented with each other. In addition, the tenth lens element L10, theeleventh lens element L11, and the twelfth lens element L12 are cementedwith each other.

The fourth lens unit G4, in order from the object side to the imageside, includes: a bi-concave fourteenth lens element L14; a bi-convexfifteenth lens element L15; and a negative meniscus sixteenth lenselement L16 with the convex surface facing the object side. Thefourteenth lens element L14 and the fifteenth lens element L15 arecemented with each other. A surface of the sixteenth lens element L16facing the image side is aspheric.

At the time of zooming, the respective lens units move along the opticalaxis such that: the interval between the first lens unit G1 and thesecond lens unit G2 at a telephoto limit is made shorter than theinterval at a wide-angle limit; the interval between the second lensunit G2 and the third lens unit G3 at a telephoto limit is made shorterthan the interval at a wide-angle limit; and the interval between thethird lens unit G3 and the fourth lens unit G4 at a telephoto limit ismade longer than the interval at a wide-angle limit. More specifically,at the time of zooming from a wide-angle limit to a telephoto limit, thefirst lens unit G1 moves to the image side along the optical axis,whereas the second lens unit G2, the third lens unit G3, and the fourthlens unit G4 move to the object side along the optical axis. Theaperture diaphragm A moves to the object side together with the secondlens unit G2.

Further, at the time of focusing from an infinity in-focus condition toa close-point in-focus condition, the second lens unit G2 moves to theimage side along the optical axis.

The following description is given for conditions to be satisfied by thezoom lens system according to each embodiment. Here, in the zoom lenssystem according to each embodiment, a plurality of conditions to besatisfied are set forth. Thus, a configuration of the zoom lens systemthat satisfies as many applicable conditions as possible is mostpreferable. However, when an individual condition is satisfied, a zoomlens system having a corresponding effect can be obtained.

In the zoom lens system according to the respective embodiments, it ispreferable that the following condition is satisfied.

−0.65<f _(W) /f ₁<−0.45  (1)

where,

f₁ is a focal length of the first lens unit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (1) sets forth the ratio between the focal length of theentire system and the focal length of the first lens unit. When thevalue exceeds the upper limit of the condition (1), it becomes difficultto compensate the astigmatism or the distortion, which causes difficultyin achieving preferable optical performance in the periphery part of theimage. Further, when the value goes below the lower limit of thecondition (1), the entire length of the lenses increases, and inaddition, the diameter of the first lens unit increases. Thus, itbecomes difficult to achieve the size reduction.

In the zoom lens system according to the respective embodiments, it ispreferable that the following condition is satisfied.

0.1<f _(W) /f ₂<0.3  (2)

where,

f₂ is a focal length of the second lens unit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (2) sets forth the ratio between the focal length of theentire system and the focal length of the second lens unit. When thevalue exceeds the upper limit of the condition (2), the entire length ofthe lenses increases, and it becomes difficult to achieve the sizereduction. At the same time, it becomes difficult to preferablycompensate a so-called coma aberration in a range from a middle positionto a telephoto limit. Further, when the value goes below the lower limitof the condition (2), there is no effect of the field curvaturecompensation, which is obtained by imparting the refractive power to thesecond lens unit and to the subsequent third lens unit and changing theinterval therebetween by zooming. Thus, it becomes difficult to achievethe preferable optical performance in the periphery part of the image.

In the zoom lens system according to the respective embodiments, it ispreferable that the following condition is satisfied.

0.25<f _(W) /f ₃<0.5  (3)

where,

f₃ is a focal length of the third lens unit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (3) sets forth the ratio between the focal length of theentire system and the focal length of the third lens unit. When thevalue exceeds the upper limit of the condition (3), it becomes difficultto compensate the spherical aberration or the coma aberration whichrelates to the optical performance on and around the optical axis, andin addition, the intervals between third lens unit and the lens unitsbefore and after the third lens unit become insufficient, which causesdifficulty in configuring the zoom lens system. Further, when the valuegoes below the lower limit of the condition (3), the amount of movementof the third lens unit increases at the time of variation ofmagnification, and thus it becomes difficult to achieve the sizereduction.

In the zoom lens system according to the respective embodiments, it ispreferable that the following condition is satisfied.

−0.1<f _(W) /f ₄<−0.05  (4)

where,

f₄ is a focal length of the fourth lens unit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (4) sets forth the ratio between the focal length of theentire system and the focal length of the fourth lens unit. When thevalue exceeds the upper limit of the condition (4), a change in theastigmatism or the like caused by the decentering error or the like ofthe fourth lens unit increases. In addition, since the positive opticalpower of the third lens unit on the object side relative to the fourthlens unit increase, a change in the coma aberration caused by thedecentering error or the like of the third lens unit is apt to increase.Thus, the situation is not preferable since costs necessary formanufacturing increase. Further, when the value goes below the lowerlimit of the condition (4), the amount of movement of the fourth lensunit at the time of focusing increases, and thus it becomes difficult toachieve the size reduction.

In the zoom lens system according to the respective embodiments, it ispreferable that the following condition is satisfied.

0.01<f _(W) /f ₅<0.15  (5)

where,

f₅ is a focal length of the fifth lens unit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (5) sets forth the ratio between the focal length of theentire system and the focal length of the fifth lens unit. When thevalue exceeds the upper limit of the condition (5), the zoom lens systemis approximate to the true telecentric condition. Thus, the diameter ofthe fifth lens unit increases, and as a result it becomes difficult toachieve the size reduction. Further, when the value goes below the lowerlimit of the condition (5), the zoom lens system is deviated from thetelecentric condition, and in particular, the incident angle of light tobe incident on the periphery part of the image sensor increases, andthus this situation is unpreferable in terms of characteristics of theimage sensor.

In the zoom lens system according to the respective embodiments, it ispreferable that the following condition is satisfied.

DIS_(W)<−8  (6)

where,

DIS_(W) is distortion (%) at the maximum image height at a wide-anglelimit.

The distortion DIS_(W) can be obtained from the following formula.

DIS_(W)=(Y′−Y)/Y×100(unit: %)

(where, Y′ is a real image height, and Y is an ideal image height).

When the value exceeds the upper limit of the condition (6), thedistortion is compensated excessively, and it becomes difficult tocompensate the coma aberration or the astigmatism. Thus, it becomesdifficult to achieve the size reduction.

In the zoom lens system according to the respective embodiments, it ispreferable that the following condition is satisfied.

2.3<(R ₁₁ +R ₁₂)/(R ₁₁ −R ₁₂)<10  (7)

where,

R₁₁ is an object side curvature radius of the lens element closest tothe object side in the first lens unit, and

R₁₂ is an image side curvature radius of the lens element closest to theobject side in the first lens unit.

The condition (7) sets forth the shape of the lens element closest tothe object side in the first lens unit. When the value exceeds the upperlimit of the condition (7), the diameter of the lens element increases,and it becomes difficult to process the lens element. Thus, it becomesdifficult to achieve the size reduction, and at the same time, themanufacturing costs increase. Further, when the value goes below thelower limit of the condition (7), a large negative distortion isgenerated, and thus this leads to insufficient compensation of thedistortion.

In the zoom lens system according to the respective embodiments, it ispreferable that the following condition is satisfied.

2.3<(R ₂₁ +R ₂₂)/(R ₂₁ −R ₂₂)<10  (8)

where,

R₂₁ is an object side curvature radius of the second lens element fromthe object side in the first lens unit, and

R₂₂ is an image side curvature radius of the second lens element fromthe object side in the first lens unit.

The condition (8) sets forth the shape of the second lens element fromthe object side in the first lens unit. When the value exceeds the upperlimit of the condition (8), the diameter of the lens element increases,and it becomes difficult to process the lens element. Thus, it becomesdifficult to achieve the size reduction, and at the same time, themanufacturing costs increase. Further, when the value goes below thelower limit of the condition (8), a large negative distortion isgenerated, and thus this leads to insufficient compensation of thedistortion.

In the zoom lens system according to the respective embodiment, it ispreferable that the following condition is satisfied.

2.3<(R ₃₁ +R ₃₂)/(R ₃₁ −R ₃₂)<10  (9)

where,

R₃₁ is an object side curvature radius of the third lens element fromthe object side in the first lens unit, and

R₃₂ is an image side curvature radius of the third lens element from theobject side in the first lens unit.

The condition (9) sets forth the shape of the third lens element fromthe object side in the first lens unit. When the value exceeds the upperlimit of the condition (9), the diameter of the lens element increases,and it becomes difficult to process the lens element. Thus, it becomesdifficult to achieve the size reduction, and at the same time, themanufacturing costs increases. Further, when the value goes below thelower limit of the condition (9), a large negative distortion isgenerated, and thus this leads to insufficient compensation of thedistortion.

In the zoom lens system according to the respective embodiments, it ispreferable that the following condition is satisfied.

1.4<DL/YM<2.5  (10)

(where, 100<2ω_(W)<140) where,

DL is an effective diameter of the lens surface closest to the imageside,

YM is the maximum image height at a wide-angle limit, and

ω_(W) is a half view angle (°) at a wide-angle limit.

The condition (10) sets forth the ratio between the effective diameterof the lens surface closest to the image side and the maximum imageheight. When the value exceeds the upper limit of the condition (10),the diameter of the lens closest to the image side increases, and itbecomes difficult to achieve the size reduction. Further, when the valuegoes below the lower limit of the condition (10), the back focus needsto be elongated in order to avoid an increase in the incident angle oflight. Thus, it becomes difficult to achieve the size reduction.

In the zoom lens system according to the respective embodiments, it ispreferable that the following condition is satisfied.

1.2<BF_(W) /YM<1.6  (11)

where,

BF_(W) is the back focus at a wide-angle limit,

YM is the maximum image height at a wide-angle limit, and

ω_(W) is a half view angle (°) at a wide-angle limit.

The condition (11) sets forth the ratio between the back focus at awide-angle limit and the maximum image height. When the value exceedsthe upper limit of the condition (11), the zoom lens system exhibits asignificant retrofocus characteristic, which causes difficulty incompensating the distortion. Thus, it becomes difficult to achieve thesize reduction. Further, when the value goes below the lower limit ofthe condition (11), the shadow of foreign particles (dust) adhering tothe surface of the lens closest to the image side becomes significant onthe taken image. Thus, handling of the interchangeable lens apparatusbecomes complicated. For example, adherence of foreign particles needsto be carefully checked at the time of changing the lens system.

Here, the lens units constituting the zoom lens system of the respectiveembodiments may be composed exclusively of refractive type lens elementsthat deflect the incident light by refraction (that is, lenses of a typein which deflection is achieved at the interface between media eachhaving a distinct refractive index). Alternatively, the lens units mayemploy any one of or a combination of some of: diffractive type lenselements that deflect the incident light by diffraction;refractive-diffractive hybrid type lens elements or the like thatdeflect the incident light by a combination of diffraction andrefraction; and gradient index type lens elements that deflect theincident light by distribution of refractive index in the medium.

Embodiment 7

FIG. 13 is a schematic construction diagram of an interchangeable-lenstype digital camera system according to Embodiment 7.

A interchangeable-lens type digital camera system 100 (hereinafter,simply referred to as “camera system”) according to the presentembodiment includes a camera body 101, and an interchangeable lensapparatus 201 connected to the camera body 101 in an attachable andremovable manner.

The camera body 101 includes an image sensor 102 which receives anoptical image formed by a zoom lens system 202 of the interchangeablelens apparatus 201 thereby to convert the optical image into an electricimage signal, a liquid crystal display monitor 103 which displays animage signal converted by the image sensor 102, and a camera mountsection 104. On the other hand, the interchangeable lens apparatus 201includes the zoom lens system 202 according to any one of Embodiments 1to 6, a lens barrel which holds the zoom lens system 202, and a lensmount section 204 connected to the camera mount section 104 of thecamera body. The camera mount section 104 and the lens mount section 204are connected to each other not only physically but also electrically,and function as interfaces. That is, a controller (not shown) inside thecamera body 101 is electrically connected to a controller (not shown)inside the interchangeable lens apparatus 201, thereby achieving mutualsignal communication.

The camera system 100 according to the present embodiment includes thezoom lens system 202 according to any one of Embodiments 1 to 6, andhence is capable of displaying an preferable optical image at the timeof focusing in a live view state.

EXAMPLES

Hereinafter, numerical examples will be described below in which thezoom lens systems according to Embodiments 1 to 6 are implementedspecifically. As will be described later, Numerical Examples 1 to 6corresponds to Embodiments 1 to 6, respectively. Here, in each numericalexample, the units of the length are all “mm”, while the units of theview angle are all “°”. Moreover, in the numerical examples, r is theradius of curvature, d is the axial distance, nd is the refractive indexto the d-line, and vd is the Abbe number to the d-line. In the numericalexamples, the surfaces marked with “*” are aspheric surfaces, and theaspheric surface configuration is defined by the following formula.

$Z = {\frac{h^{2}/r}{1 + \sqrt{1 - {\left( {1 + \kappa} \right)\left( {h/r} \right)^{2}}}} + {\sum\; {A_{n}h^{n}}}}$

Here, the symbols in the formula indicate the following quantities:Z is the distance from an on-the-aspheric-surface point at a height hrelative to the optical axis to a tangential plane at the top of theaspheric surface;h is the height relative to the optical axis;r is the radius of curvature at the top;κ is the conic constant; andAn is the n-th order aspheric coefficient.

FIGS. 2, 4, 6, 8, 10, and 12 are longitudinal aberration diagrams of aninfinity in-focus condition of the zoom lens systems according toNumerical Examples 1, 2, 3, 4, 5, and 6.

In each longitudinal aberration diagram, part (a) shows the aberrationat a wide-angle limit, part (b) shows the aberration at a middleposition, and part (c) shows the aberration at a telephoto limit. Eachlongitudinal aberration diagram, in order from the left-hand side, showsthe spherical aberration (SA (mm)), the astigmatism (AST (mm)), and thedistortion (DIS (%)). In each spherical aberration diagram, the verticalaxis indicates the F-number (in each diagram, indicated as F), the solidline, the short dash line, and the long dash line indicate thecharacteristics to the d-line, the F-line, and the C-line, respectively.In each astigmatism diagram, the vertical axis indicates the imageheight (in each diagram, indicated as H), the solid line and the dashline indicate the characteristics to the sagittal image plane (in eachdiagram, indicated as “s”) and the meridional image plane (in eachdiagram, indicated as “m”), respectively.

Numerical Example 1

The zoom lens system of Numerical Example 1 corresponds to Embodiment 1shown in FIG. 1. Data of the zoom lens system according to NumericalExample 1, i.e., the surface data, the aspherical data, the variousdata, the lens element data, the zoom lens unit data, and the zoom lensunit magnification are shown in Table 1, Table 2, Table 3, Table 4,Table 5, and Table 6, respectively.

TABLE 1 (Surface data) Surface number r d nd vd Object surface ∞  132.61610 2.00000 1.80420 46.5  2 20.03180 6.25890  3 28.62190 1.800001.80420 46.5  4 16.57000 2.64120  5 20.52130 1.70000 1.80800 40.9  6*11.47060 7.78130  7 −302.25460 1.05000 1.49700 81.6  8 17.88820 0.26000 9 18.09470 4.00840 1.80610 33.3 10 60.79620 Variable 11 19.248000.70000 1.74330 49.2 12 6.77140 2.24910 1.67270 32.2 13 170.511201.89140 14 (Diaphragm) ∞ Variable 15 3979.65950 0.70000 1.84666 23.8 1613.78260 2.33950 1.51680 64.2 17 −21.54820 1.31900 18 −9.53570 0.800001.51680 64.2 19 21.19960 2.89150 1.49700 81.6 20 −15.02470 0.20000 21−58.86510 1.97180 1.49700 81.6 22 −20.72310 0.20000 23 41.66740 3.234301.49700 81.6 24 −20.80500 Variable 25 26.65630 0.80000 1.51823 59.0 2617.53640 Variable 27 84.08090 0.90000 1.80518 25.5 28 27.44430 3.577201.52300 70.1 29* −39.99340 BF Image surface ∞

TABLE 2 (Aspherical data) Surface No. Parameters 6 K = −4.01413E−01, A4= −2.82803E−05, A6 = −1.13654E−07, A8 = −7.54243E−10, A10 = 5.36525E−12,A12 = −3.87978E−14 29 K = 0.00000E+00, A4 = 5.16711E−05, A6 =2.64198E−07, A8 = −6.34113E−09, A10 = 9.00687E−11, A12 = −4.31222E−13

TABLE 3 (Various data) Zooming ratio 1.89190 Wide Middle Telephoto Focallength 7.2006 9.9053 13.6229 F-number 4.00268 3.85380 4.09472 View angle59.0156 48.7020 38.1410 Image height 10.8150 10.8150 10.8150 Overalllength of lens 95.5429 90.8643 89.7896 system BF 15.38321 15.3886015.39895 d10 19.2075 9.1749 1.9157 d14 1.9913 2.0522 1.2990 d24 2.52612.0100 1.8500 d26 5.1612 10.9650 18.0524 Entrance pupil position 19.807818.7380 17.5657 Exit pupil position −50.9354 −68.0300 −85.0516 Frontprincipal point 26.2266 27.4671 29.3411 position Back principal point88.3423 80.9590 76.1668 position

TABLE 4 (Lens element data) Unit Initial surface No. Focal length 1 1−69.4814 2 3 −52.4229 3 5 −35.1378 4 7 −33.9445 5 9 30.6741 6 11−14.3986 7 12 10.4247 8 15 −16.3366 9 16 16.6409 10 18 −12.6150 11 1918.1737 12 21 63.2652 13 23 28.4087 14 25 −101.9601 15 27 −50.9622 16 2831.6971

TABLE 5 (Zoom lens unit data) Front Initial surface Length of lensprincipal Back principal Unit No. Focal length unit point position pointposition 1 1 −14.89596 27.49980 9.27046 14.76759 2 11 40.61921 4.84050−0.45077 0.77074 3 15 22.48920 13.65610 11.20519 17.60033 4 25−101.96007 0.80000 1.58769 1.84449 5 27 80.78660 4.47720 2.60670 4.21608

TABLE 6 (Zoom lens unit magnification) Initial surface Unit No. WideMiddle Telephoto 1 1 0.00000 0.00000 0.00000 2 11 −7.04498 9.519593.52410 3 15 0.06774 −0.06597 −0.23278 4 25 1.25623 1.31323 1.38290 5 270.80635 0.80628 0.80616

Numerical Example 2

The zoom lens system of Numerical Example 2 corresponds to Embodiment 2shown in FIG. 3. Data of the zoom lens system according to NumericalExample 2, i.e., the surface data, the aspherical data, the variousdata, the lens element data, the zoom lens unit data, and the zoom lensunit magnification are shown in Table 7, Table 8, Table 9, Table 10,Table 11, and Table 12, respectively.

TABLE 7 (Surface data) Surface number r d nd vd Object surface ∞  132.47020 2.00000 1.80420 46.5  2 20.03180 6.27370  3 28.59860 1.800001.80420 46.5  4 16.57000 2.70090  5 20.52130 1.70000 1.80800 40.9  6*11.44550 8.07250  7 −100.75020 1.00000 1.49700 81.6  8 19.58010 4.004101.80610 33.3  9 92.88670 Variable 10 18.85950 0.70000 1.74330 49.2 116.74340 2.25040 1.67270 32.2 12 116.25340 1.89560 13 (Diaphragm) ∞Variable 14 595.95060 0.70000 1.84666 23.8 15 13.82680 2.34620 1.5168064.2 16 −21.12650 1.32080 17 −9.70390 0.80000 1.51680 64.2 18 20.990802.87260 1.49700 81.6 19 −15.71880 0.20000 20 −58.64710 1.97850 1.4970081.6 21 −20.62270 0.20000 22 41.46940 3.23800 1.49700 81.6 23 −20.82360Variable 24 26.64750 0.80000 1.51823 59.0 25 17.53290 Variable 2681.82020 0.90000 1.80518 25.5 27 27.27070 3.58130 1.52300 70.1 28*−40.37930 BF Image surface ∞

TABLE 8 (Aspherical data) Sur- face No. Parameters 6 K = −3.93507E−01,A4 = −2.91092E−05, A6 = −9.83771E−08, A8 = −1.09494E−09, A10 =7.89710E−12, A12 = −4.73408E−14 28 K = 0.00000E+00, A4 = 5.27176E−05, A6= 2.51049E−07, A8 = −5.97520E−09, A10 = 8.53715E−11, A12 = −4.07934E−13

TABLE 9 (Various data) Zooming ratio 1.88982 Wide Middle Telephoto Focallength 7.2052 9.9040 13.6166 F-number 4.00224 3.85285 4.09430 View angle59.1763 48.7875 38.1653 Image height 10.8150 10.8150 10.8150 Overalllength of lens 95.5329 90.8882 89.8292 system BF 15.38680 15.3904515.40348 d9 19.1344 9.1208 1.8888 d13 1.9956 2.0689 1.2998 d23 2.51082.0100 1.8500 d25 5.1707 10.9634 18.0525 Entrance pupil position 19.835218.7716 17.6109 Exit pupil position −50.5737 −67.7646 −84.7428 Frontprincipal point 26.2533 27.4959 29.3761 position Back principal point88.3277 80.9842 76.2125 position

TABLE 10 (Lens element data) Unit Initial surface No. Focal length 1 1−70.0446 2 3 −52.4889 3 5 −34.9551 4 7 −32.8954 5 8 30.0453 6 10−14.4782 7 11 10.5544 8 14 −16.7280 9 15 16.5496 10 17 −12.7277 11 1818.5672 12 20 62.9126 13 22 28.3825 14 24 −101.9672 15 26 −51.1776 16 2731.6996

TABLE 11 (Zoom lens unit data) Front Initial surface Length of lensprincipal Back principal Unit No. Focal length unit point position pointposition 1 1 −14.90085 27.55120 9.28790 14.66851 2 10 42.30042 4.84600−0.60680 0.62440 3 14 22.37367 13.65610 11.04562 17.23657 4 24−101.96715 0.80000 1.58811 1.84491 5 26 80.34236 4.48130 2.56393 4.17322

TABLE 12 (Zoom lens unit magnification) Initial surface Unit No. WideMiddle Telephoto 1 1 0.00000 0.00000 0.00000 2 10 −10.54686 7.046683.19613 3 14 0.04533 −0.08923 −0.25690 4 24 1.25690 1.31376 1.38348 5 260.80465 0.80460 0.80444

Numerical Example 3

The zoom lens system of Numerical Example 3 corresponds to Embodiment 3shown in FIG. 5. Data of the zoom lens system according to NumericalExample 3, i.e., the surface data, the aspherical data, the variousdata, the lens element data, the zoom lens unit data, and the zoom lensunit magnification are shown in Table 13 Table 14, Table 15, Table 16,Table 17, and Table 18, respectively.

TABLE 13 (Surface data) Surface number r d nd vd Object surface ∞  130.44780 2.00000 1.80420 46.5  2 18.87500 7.34890  3 27.75750 1.927801.80420 46.5  4 16.42880 3.26840  5 19.60000 1.55000 1.80470 41.0  6*10.89970 7.72330  7 −225.11440 1.89310 1.49700 81.6  8 16.32060 3.991701.80610 33.3  9 57.99910 Variable 10 18.84770 0.70000 1.72342 38.0 116.23040 2.36850 1.68400 31.3 12 115.54490 1.70700 13 (Diaphragm) ∞Variable 14 ∞ 0.70000 1.84666 23.8 15 13.71240 4.78040 1.51823 59.0 16−15.01690 1.13690 17 −8.82940 0.80000 1.51680 64.2 18 104.27750 3.148001.49700 81.6 19 −12.21860 0.20000 20 33.45760 3.28830 1.49700 81.6 21−21.12350 Variable 22 30.94380 1.00000 1.58144 40.9 23 19.52960 Variable24 −73.91420 1.00000 1.80518 25.5 25 123.34430 3.41370 1.52500 70.3 26*−19.50200 BF Image surface ∞

TABLE 14 (Aspherical data) Sur- face No. Parameters 6 K = −5.49068E−01,A4 = −1.42254E−05, A6 = −1.04715E−07, A8 = −1.46986E−10, A10 =3.11013E−12, A12 = −2.87242E−14 26 K = 0.00000E+00, A4 = 8.23200E−05, A6= −7.52604E−08, A8 = 6.50947E−09, A10 = −9.16057E−11, A12 = 4.80195E−13

TABLE 15 (Various data) Zooming ratio 1.88906 Wide Middle TelephotoFocal length 7.2009 9.9186 13.6030 F-number 4.03569 3.88161 4.13870 Viewangle 58.9271 47.9004 37.3032 Image height 10.8150 10.8150 10.8150Overall length of lens 96.5585 92.8958 92.3358 system BF 15.3827315.38116 15.38602 d9 18.0260 8.4931 1.4460 d13 1.7982 2.1728 1.6710 d212.4078 1.7000 1.7108 d23 4.9978 11.2027 18.1760 Entrance pupil position20.4341 19.4466 18.3521 Exit pupil position −58.3885 −89.5091 −126.2034Front principal point 26.9321 28.4273 30.6482 position Back principalpoint 89.3576 82.9771 78.7328 position

TABLE 16 (Lens element data) Unit Initial surface No. Focal length 1 1−66.9043 2 3 −54.1627 3 5 −33.1474 4 7 −30.5391 5 8 27.0196 6 10−13.1720 7 11 9.5439 8 14 −16.1958 9 15 14.6636 10 17 −15.7133 11 1822.2055 12 20 26.5851 13 22 −94.0884 14 24 −57.2713 15 25 32.3410

TABLE 17 (Zoom lens unit data) Front Initial surface Length of lensprincipal Back principal Unit No. Focal length unit point position pointposition 1 1 −14.40374 29.70320 10.19859 16.32686 2 10 37.60170 4.77550−0.50091 0.78179 3 14 22.69792 14.05360 11.13540 17.51424 4 22 −94.088381.00000 1.77131 2.11793 5 24 68.03402 4.41370 5.03396 6.83127

TABLE 18 (Zoom lens unit magnification) Initial surface Unit No. WideMiddle Telephoto 1 1 0.00000 0.00000 0.00000 2 10 −4.88114 20.553814.23608 3 14 0.10003 −0.03110 −0.19604 4 22 1.26498 1.33090 1.40509 5 240.80943 0.80945 0.80938

Numerical Example 4

The zoom lens system of Numerical Example 4 corresponds to Embodiment 4shown in FIG. 7. Data of the zoom lens system according to NumericalExample 4, i.e., the surface data, the aspherical data, the variousdata, the lens element data, the zoom lens unit data, and the zoom lensunit magnification are shown in Table 19, Table 20, Table 21, Table 22,Table 23, and Table 24, respectively.

TABLE 19 (Surface data) Surface number r d nd vd Object surface ∞  133.73000 2.00000 1.80420 46.5  2 20.50000 5.85990  3 26.77380 1.800001.80420 46.5  4 16.10000 4.64310  5 19.60000 1.55000 1.80470 41.0  6*10.69470 8.26910  7 −298.88690 1.26450 1.49700 81.6  8 16.57410 5.667701.80610 33.3  9 58.84120 Variable 10 19.49320 0.70000 1.72342 38.0 117.80550 4.16820 1.68400 31.3 12* 65.51100 1.50600 13 (Diaphragm) ∞Variable 14 268.54290 0.70000 1.84666 23.8 15 18.67540 2.51990 1.5182359.0 16 −12.40510 0.78790 17 −9.47110 0.80000 1.51680 64.2 18 12.004203.75020 1.49700 81.6 19 −17.26890 0.20000 20 38.76770 2.94440 1.4970081.6 21 −18.34760 Variable 22 33.88100 1.00000 1.58144 40.9 23 19.79670Variable 24 −205.25430 1.00000 1.80518 25.5 25 58.31210 3.35500 1.5250070.3 26* −23.17480 BF Image surface ∞

TABLE 20 (Aspherical data) Sur- face No. Parameters 6 K = −4.41439E−01,A4 = −3.54100E−05, A6 = 1.15587E−07, A8 = −3.74110E−09, A10 =2.31717E−11, A12 = −9.50173E−14 12 K = 0.00000E+00, A4 = 4.91209E−05, A6= −2.40723E−06, A8 = 1.65752E−07, A10 = −4.61598E−09, A12 = 0.00000E+0026 K = 0.00000E+00, A4 = 7.10598E−05, A6 = 6.08469E−08, A8 =−1.63689E−09, A10 = 4.66337E−11, A12 = −2.92076E−13

TABLE 21 (Various data) Zooming ratio 1.88910 Wide Middle TelephotoFocal length 7.2001 9.8960 13.6017 F-number 4.05005 4.05027 4.05142 Viewangle 58.9987 48.4820 37.6168 Image height 10.8150 10.8150 10.8150Overall length of lens 96.4352 91.3849 91.2929 system BF 15.3725515.84598 15.85089 d9 17.9459 8.0821 1.5843 d13 2.1001 1.9877 1.1500 d211.7000 2.0393 1.7000 d23 4.8308 8.9439 16.5218 Entrance pupil position20.1706 19.2415 18.3453 Exit pupil position −39.9985 −51.4394 −71.3834Front principal point 26.4345 27.6821 29.8262 position Back principalpoint 89.2352 81.4889 77.6912 position

TABLE 22 (Lens element data) Unit Initial surface No. Focal length 1 1−69.6856 2 3 −54.2988 3 5 −31.7123 4 7 −31.5544 5 8 27.0070 6 10−18.4597 7 11 12.5859 8 14 −23.7367 9 15 14.7927 10 17 −10.1157 11 1814.8816 12 20 25.4941 13 22 −84.1001 14 24 −56.3032 15 25 32.0423

TABLE 23 (Zoom lens unit data) Front Initial surface Length of lensprincipal Back principal Unit No. Focal length unit point position pointposition 1 1 −14.24164 31.05430 9.85997 16.74252 2 10 44.08317 6.37420−1.41896 0.69708 3 14 21.93528 11.70240 8.51387 12.79729 4 22 −84.100101.00000 1.56191 1.91263 5 24 69.44057 4.35500 4.15667 5.84080

TABLE 24 (Zoom lens unit magnification) Initial Unit surface No. WideMiddle Telephoto 1 1 0.00000 0.00000 0.00000 2 10 −44.20775 4.971812.86917 3 14 0.01098 −0.12954 −0.28937 4 22 1.30241 1.36019 1.45039 5 240.80002 0.79320 0.79313

Numerical Example 5

The zoom lens system of Numerical Example 5 corresponds to Embodiment 5shown in FIG. 9. Data of the zoom lens system according to NumericalExample 5, i.e., the surface data, the aspherical data, the variousdata, the lens element data, the zoom lens unit data, and the zoom lensunit magnification are shown in Table 25, Table 26, Table 27, Table 28,Table 29, and Table 30, respectively.

TABLE 25 (Surface data) Surface number r d nd vd Object surface ∞  132.53230 2.00000 1.80420 46.5  2 20.50000 5.29920  3 24.93130 1.800001.80420 46.5  4 16.00000 6.77330  5 30.03360 1.93360 1.80470 41.0  6*14.19960 6.83460  7 −81.80750 1.29550 1.49700 81.6  8 29.31440 4.066701.80610 33.3  9 213.26320 Variable 10 19.05720 0.70000 1.72623 54.8 116.93710 3.42900 1.63182 34.7 12* 696.48680 1.35570 13 (Diaphragm) ∞Variable 14 −631.44520 0.70000 1.84666 23.8 15 17.41730 2.50600 1.5359450.3 16 −12.21090 1.02130 17 −7.38790 0.80000 1.51742 52.1 18 24.344304.39930 1.49700 81.6 19 −10.50450 0.20000 20 55.10800 3.00710 1.4970081.6 21 −19.57410 Variable 22 40.60470 1.00000 1.58144 40.9 23 23.96040Variable 24 233.55820 1.00000 1.80518 25.5 25 34.11090 0.77000 2679.43180 2.32080 1.52500 70.3 27* −28.67840 BF Image surface ∞

TABLE 26 (Aspherical data) Surface No. Parameters 6 K = 0.00000E+00, A4= −4.43286E−05, A6 = −1.05536E−07, A8 = −2.37863E−09, A10 = 1.94014E−11,A12 = −8.16832E−14 12 K = 0.00000E+00, A4 = −3.18703E−07, A6 =−1.05633E−06, A8 = −1.75650E−08, A10 = 0.00000E+00, A12 = 0.00000E+00 27K = 0.00000E+00, A4 = 6.73656E−05, A6 = 4.76084E−07, A8 = −6.30642E−09,A10 = 5.53166E−11, A12 = 0.00000E+00

TABLE 27 (Various data) Zooming ratio 1.88916 Wide Middle TelephotoFocal length 7.2007 9.8948 13.6032 F-number 4.05157 4.05172 4.05114 Viewangle 59.0196 48.8263 38.1892 Image height 10.8150 10.8150 10.8150Overall length of lens 98.5596 90.7884 87.2555 system BF 15.3699615.68211 15.43608 d9 20.5242 9.1837 1.4783 d13 3.0469 2.6786 1.4085 d211.9738 2.0576 1.7000 d23 4.4326 7.9743 14.0205 Entrance pupil position21.2510 20.1148 18.9129 Exit pupil position −42.7313 −46.3055 −48.8643Front principal point 27.5593 28.4301 29.6382 position Back principalpoint 91.3589 80.8936 73.6523 position

TABLE 28 (Lens element data) Unit Initial surface No. Focal length 1 1−74.4367 2 3 −61.0190 3 5 −35.3977 4 7 −43.2556 5 8 41.7491 6 10−15.3935 7 11 11.0686 8 14 −20.0096 9 15 13.8012 10 17 −10.8607 11 1815.4108 12 20 29.4558 13 22 −102.8018 14 24 −49.7209 15 26 40.4334

TABLE 29 (Zoom lens unit data) Front Initial surface Length of lensprincipal Back principal Unit No. Focal length unit point position pointposition 1 1 −14.95255 30.00290 10.49730 16.54644 2 10 41.90590 5.48470−0.32700 1.30559 3 14 20.56078 12.63370 9.79278 15.07317 4 22 −102.801831.00000 1.57746 1.93084 5 24 181.29625 4.09080 8.72778 10.25289

TABLE 30 (Zoom lens unit magnification) Initial Unit surface No. WideMiddle Telephoto 1 1 0.00000 0.00000 0.00000 2 10 −6.25432 9.031083.39440 3 14 0.06686 −0.06181 −0.21607 4 22 1.21332 1.25115 1.30730 5 240.94921 0.94749 0.94885

Numerical Example 6

The zoom lens system of Numerical Example 6 corresponds to Embodiment 6shown in FIG. 11. Data of the zoom lens system according to NumericalExample 6, i.e., the surface data, the aspherical data, the variousdata, the lens element data, the zoom lens unit data, and the zoom lensunit magnification are shown in Table 31, Table 32, Table 33, Table 34,Table 35, and Table 36, respectively.

TABLE 31 (Surface data) Surface number r d nd vd Object surface ∞  130.26100 2.00000 1.80420 46.5  2 19.23600 7.05290  3* 43.33240 2.000001.80470 41.0  4 17.35190 4.41100  5 30.05900 1.00000 1.80420 46.5  611.70510 7.37650  7 −36.01870 1.50000 1.60602 57.4  8* −132.959500.20000  9 26.63140 2.31620 1.92286 20.9 10 57.60560 Variable 11*50.16330 1.55520 1.68400 31.3 12 −748.57270 4.22080 13 (Diaphragm) ∞Variable 14 21.62730 2.96530 1.55920 53.9 15 −13.58820 0.70000 1.8061033.3 16 21.60250 2.41110 1.84666 23.8 17 −29.87500 0.15000 18 36.465301.95480 1.49700 81.6 19 −40.39410 0.70000 1.80610 33.3 20 11.759803.61880 1.49700 81.6 21 −50.54280 0.68720 22 −137.65940 1.81280 1.5891361.3 23 −31.54950 Variable 24 −52.47270 0.70000 1.75520 27.5 25 75.521003.36870 1.56384 60.8 26 −18.57000 0.15000 27 106.05390 1.20000 1.8047041.0 28* 43.21760 BF Image surface ∞

TABLE 32 (Aspherical data) Surface No. Parameters 3 K = 0.00000E+00, A4= 3.85974E−05, A6 = −5.79936E−08, A8 = −1.32058E−11, A10 = 1.06809E−12,A12 = −2.06927E−15 8 K = 0.00000E+00, A4 = 1.93728E−06, A6 =−3.18981E−07, A8 = 1.51649E−09, A10 = 8.06356E−13, A12 = −1.02174E−13 11K = 0.00000E+00, A4 = −1.75155E−05, A6 = −2.03856E−07, A8 = 7.42728E−09,A10 = 0.00000E+00, A12 = 0.00000E+00 28 K = 0.00000E+00, A4 =4.70983E−05, A6 = 3.70787E−07, A8 = −1.10328E−08, A10 = 2.06027E−10, A12= −1.42704E−12

TABLE 33 (Various data) Zooming ratio 1.94367 Wide Middle TelephotoFocal length 7.1000 9.7001 13.8001 F-number 4.12083 4.12002 4.12038 Viewangle 59.2702 49.3156 38.2059 Image height 10.8150 10.8150 10.8150Overall length of lens 99.4483 94.2036 90.8131 system BF 19.1660820.01519 24.61319 d10 19.1587 9.3837 3.0374 d13 5.5000 5.1916 1.3500 d231.5722 5.5618 7.7612 Entrance pupil position 18.7937 18.1050 17.4533Exit pupil position −31.6025 −35.7750 −28.4490 Front principal point24.9008 26.1185 27.6644 position Back principal point 92.3482 84.503577.0130 position

TABLE 34 (Lens element data) Unit Initial surface No. Focal length 1 1−71.4288 2 3 −37.2432 3 5 −24.4306 4 7 −81.9968 5 9 51.8095 6 11 68.78677 14 15.3881 8 15 −10.2568 9 16 15.1325 10 18 38.8892 11 19 −11.2318 1220 19.5729 13 22 69.0383 14 24 −40.9006 15 25 26.7805 16 27 −91.4233

TABLE 35 (Zoom lens unit data) Front Initial surface Length of lensprincipal Back principal Unit No. Focal length unit point position pointposition 1 1 −12.26575 27.85660 9.45738 13.47547 2 11 68.78668 5.776000.05805 0.68900 3 14 25.57225 15.00000 4.32045 8.58711 4 24 284.844505.41870 10.16158 12.54028

TABLE 36 (Zoom lens unit magnification) Initial Unit surface No. WideMiddle Telephoto 1 1 0.00000 0.00000 0.00000 2 11 3.00077 2.103691.76176 3 14 −0.20142 −0.39374 −0.68040 4 24 0.95772 0.95473 0.93859

The following Tables 37 and 38 show values corresponding to theindividual conditions in the zoom lens systems of the respectivenumerical examples.

TABLE 37 (Corresponding values to individual conditions: NumericalExamples 1-4) Numerical Example Condition 1 2 3 4 (1) f_(W)/f₁ −0.483−0.484 −0.500 −0.506 (2) f_(W)/f₂ 0.177 0.170 0.192 0.163 (3) f_(W)/f₃0.320 0.322 0.317 0.328 (4) f_(W)/f₄ −0.071 −0.071 −0.077 −0.086 (5)f_(W)/f₅ 0.089 0.090 0.106 0.104 (6) DIS_(W) −9.81 −10.44 −9.50 −9.74(7) (R₁₁ + R₁₂)/(R₁₁ − R₁₂) 4.184 4.221 4.262 4.099 (8) (R₂₁ + R₂₂)/(R₂₁− R₂₂) 3.750 3.755 3.900 4.017 (9) (R₃₁ + R₃₂)/(R₃₁ − R₃₂) 3.535 3.5223.506 3.402 (10) DL/YM 1.658 1.636 1.650 1.597 (11) BF_(W)/YM 1.4221.423 1.422 1.421 2ω_(W)(°) 118.03 118.35 117.85 118.00

TABLE 38 (Corresponding values to individual conditions: NumericalExamples 5 and 6) Numerical Example Condition 5 6 (1) f_(W)/f₁ −0.482−0.579 (2) f_(W)/f₂ 0.172 0.103 (3) f_(W)/f₃ 0.350 0.278 (4) f_(W)/f₄−0.070 0.025 (5) f_(W)/f₅ 0.040 — (6) DIS_(W) −9.82 −9.45 (7) (R₁₁ +R₁₂)/(R₁₁ − R₁₂) 4.407 4.490 (8) (R₂₁ + R₂₂)/(R₂₁ − R₂₂) 4.583 2.336 (9)(R₃₁ + R₃₂)/(R₃₁ − R₃₂) 2.794 2.275 (10) DL/YM 1.444 1.368 (11)BF_(W)/YM 1.421 1.772 2ω_(W)(°) 118.04 118.54

The zoom lens system according to the present invention is applicable toa digital input device such as a digital still camera, a digital videocamera, a mobile telephone, a PDA (Personal Digital Assistance), asurveillance camera in a surveillance system, a Web camera or avehicle-mounted camera. In particular, the present zoom lens system issuitable for an imaging device in a digital still camera, a digitalvideo camera or the like that requires high image quality.

While the invention has been described in detail, the foregoingdescription is in all aspects illustrative and not restrictive. It isunderstood that numerous other modifications and variations can bedevised without departing from the scope of the invention.

1. A zoom lens system comprising a plurality of lens units andperforming zooming by changing intervals among the lens units, whereinthe plurality of lens units, in order from an object side to an imageside, includes: a first lens unit having negative optical power; asecond lens unit having positive optical power; a third lens unit havingpositive optical power; and a fourth lens, and the following conditionsare satisfied:1.4<DL/YM<2.5  (10)1.2<BF_(W) /YM<1.6  (11) (where, 100<2ω_(W)<140) where, DL is aneffective diameter of the lens surface closest to the image side, BF_(W)is the back focus at a wide-angle limit, YM is the maximum image heightat a wide-angle limit, and ω_(W) is a half view angle (°) at awide-angle limit.
 2. The zoom lens system as claimed in claim 1, whereinthe fourth lens unit has negative optical power, the zoom lens systemfurther comprises a fifth lens unit having positive optical power andarranged relative to the fourth lens unit, and at the time of zooming,the fifth lens unit is fixed.
 3. The zoom lens system as claimed inclaim 1, satisfying the following condition:DIS_(W)<−8  (6) where, DIS_(W) is distortion (%) at a maximum imageheight at a wide-angle limit.
 4. The zoom lens system as claimed inclaim 1, satisfying the following condition:−0.65<f _(W) /f ₁<−0.45  (1) where, f₁ is a focal length of the firstlens unit, and f_(W) is a focal length of an entire system at awide-angle limit.
 5. The zoom lens system as claimed in claim 1,satisfying the following condition:0.1<f _(W) /f ₂<0.3  (2) where, f₂ is a focal length of the second lensunit, and f_(W) is a focal length of an entire system at a wide-anglelimit.
 6. The zoom lens system as claimed in claim 1, satisfying thefollowing condition:0.25<f _(W) /f ₃<0.5  (3) where, f₃ is a focal length of the third lensunit, and f_(W) is a focal length of an entire system at a wide-anglelimit.
 7. The zoom lens system as claimed in claim 1, satisfying thefollowing condition:−0.1<f _(W) /f ₄<−0.05  (4) where, f₄ is a focal length of the fourthlens unit, and f_(W) is a focal length of an entire system at awide-angle limit.
 8. The zoom lens system as claimed in claim 4,satisfying the following condition:0.01<f _(W) /f ₅<0.15  (5) where, f₅ is a focal length of the fifth lensunit, and f_(W) is a focal length of an entire system at a wide-anglelimit.
 9. An interchangeable lens apparatus, comprising: a zoom lenssystem including a plurality of lens and performing zooming by changingintervals among the lens units; and a mount section connected to acamera body that includes an image sensor which receives an opticalimage formed by the zoom lens system thereby to convert the opticalimage to an electrical image signal, wherein the plurality of lensunits, in order from an object side to an image side, includes: a firstlens unit having negative optical power; a second lens unit havingpositive optical power; a third lens unit having positive optical power;and a fourth lens, and the following conditions are satisfied:1.4<DL/YM<2.5  (10)1.2<BF_(W) /YM<1.6  (11) (where, 100<2ω_(W)<140) where, DL is aneffective diameter of the lens surface closest to the image side, BF_(W)is the back focus at a wide-angle limit, YM is the maximum image heightat a wide-angle limit, and ω_(W) is a half view angle (°) at awide-angle limit.
 10. A camera system, comprising: an interchangeablelens apparatus that includes a zoom lens system including a plurality oflens units and performing zooming by changing intervals among the lensunits; and a camera body which is connected to the interchangeable lensapparatus via a camera mount section in an attachable and removablemanner and includes an image sensor which receives an optical imageformed by the zoom lens system thereby to convert the optical image toan electrical image signal, wherein the plurality of lens units, inorder from an object side to an image side, includes: a first lens unithaving negative optical power; a second lens unit having positiveoptical power; a third lens unit having positive optical power; and afourth lens, and the following conditions are satisfied:1.4<DL/YM<2.5  (10)1.2<BF_(W) /YM<1.6  (11) (where, 100<2ω_(W)<140) where, DL is aneffective diameter of the lens surface closest to the image side, BF_(W)is the back focus at a wide-angle limit, YM is the maximum image heightat a wide-angle limit, and ω_(W) is a half view angle (°) at awide-angle limit.